Remote control for a plug-dropping head

ABSTRACT

An apparatus and method of dropping a pumpdown plug or ball is revealed. The assembly can be integrally formed with a plug-dropping head or can be an auxiliary feature that is mounted to a plug-dropping head. The release mechanism is actuated by remote control, employing intrinsically safe circuitry. The circuitry, along with its self-contained power source, actuates a primary control member responsive to an input signal so as to allow component shifting for release of the pumpdown plug or ball. Multiple plug-dropping heads can be stacked, each responsive to a discrete release signal. Actuation to drop the pumpdown ball or plug is accomplished even while the components are rotating or are moving longitudinally. Using the apparatus and method of the present invention, personnel do not need to climb up in the derrick to actuate manual valves. There is additionally no need for a rig floor-mounted control panel with hydraulic lines extending from the control panel to remotely located valves for plug or ball release.

This is a divisional of application Ser. No. 08/068,513, filed on May27, 1993, now U.S. Pat. No. 5,435,390, issued Jul. 25, 1995.

FIELD OF THE INVENTION

The field of this invention relates to methods and devices usable in thefield of oil and gas exploration and production, more specificallydevices and methods related to cementing operations involving thecementing of a liner by dropping or by pumping down a plug.

BACKGROUND OF THE INVENTION

Cementing operations have involved the use of plugs as a way ofcorrectly positioning the cement when setting a liner. Some mechanismshave employed the use of pressure or vacuum to initiate plug movementdownhole for proper displacement of the cement to its appropriatelocation for securing the liner properly. The early designs were manualoperations so that when it was time to release a plug for the cementingoperation, a lever was manually operated to accomplish the dropping ofthe plug. This created several problems because the plug-dropping headwould not always be within easy access of the rig floor. Frequently,depending upon the configuration of the particular well being drilled,the dropping head could be as much as 100 ft. or more in the derrick. Inorder to properly actuate the plug to drop, rig personnel would have togo up on some lift mechanism to reach the manual handle. This processwould have to be repeated if the plug-dropping head had facilities fordropping more than one plug. In those instances, each time another plugwas to be dropped, the operator of the handle would have to be hoistedto the proper elevation for the operation. In situations involving foulweather, such as high winds or low visibility, the manual operation hadnumerous safety risks. Manual operations used in the past areillustrated in U.S. Pat. No. 4,854,383. In that patent, a manual valverealignment redirected the flow from bypassing the plug to directlyabove it so that it could be driven downhole.

Hydraulic systems involving a stationary control panel mounted on therig floor, with the ability to remotely operate valves in conjunctionwith cementing plugs, have also been used in the past. Typical of suchapplications is U.S. Pat. No. 4,782,894. Some of the drawbacks of suchsystems are that for unusual applications where the plug-dropping headturned out to be a substantial distance from the rig floor, the hosesprovided with the hydraulic system would not be long enough to reach thecontrol panel meant to be mounted on the rig floor. Instead, in order tomake the hoses deal with these unusual placement situations, the actualcontrol panel itself had to be hoisted off the rig floor. This, ofcourse, defeated the whole purpose of remote operation. Additionally,the portions of the dropping head to which the hydraulic lines wereconnected would necessarily have to remain stationary. This provedsomewhat undesirable to operators who wanted the flexibility to continuerotation as well as up or down movements during the cementing operation.Similar such remote-control hydraulic systems are illustrated in U.S.Pat. Nos. 4,427,065; 4,671,353.

Yet other systems involve the pumping of cement on the rig floor tolaunch a ball or similar object, the seating of which would urge thecementing plug to drop. Typical of such a system is U.S. Pat. No.5,095,988. U.S. Pat. No. 4,040,603 shows the general concept of aplug-release mechanism using a hydraulic circuit mounted on the rigfloor. U.S. Pat. No. 5,033,113 shows generally the concept of using aninfrared receiver to trigger the operation of a device such as anelectric fan.

One type of previously used plug-dropping head is the model TD put outby Baker Oil Tools. This device has a plug stop to retain the plug, witha shifting sleeve which in a first position allows the flow to bypassaround the plug being retained by the plug stop. Upon manual turning ofa set screw, the sleeve shifts, allowing the plug stop to pivot so thatthe plug is released. The shifting of the sleeve also closes the bypassaround the sleeve and forces pressure on top of the plug so that it isdriven down into the wellbore in the cementing operation.

The apparatus of the present invention has been designed to achieveseveral objectives. By putting together an assembly that can be actuatedby remote control from a safe location on the rig floor, the safetyaspects of plug dropping have been improved. No longer will an operatorbe required to go up in the derrick to actuate a single or multiplelevers in the context of liner cementing. Use of the apparatus andmethod of the present invention also eliminates numerous hydraulic hosesthat need to be extended from a control panel to the final elementnecessary to be operated to allow the plug to drop. The plug can bedropped while the rotary table is in operation such that not onlyrotation but movement into and out of the wellbore is possible as theplug is being released to drop. The equipment is designed to beintrinsically safe to avoid any possibility of creation of a spark whichcould trigger an explosion. The equipment is compact and economicallyaccomplishes the plug-dropping maneuver while the operator stands in asafe location on the rig floor. The actuation to drop can beaccomplished on the fly while the plug-dropping head is being rotated orbeing moved longitudinally. Plug-dropping heads can be used in tandemand be made to respond to discrete signals. This ensures that the plugsare released in the proper order from a safe location on the rig.

SUMMARY OF THE INVENTION

An apparatus and method of dropping a pumpdown plug or ball is revealed.The assembly can be integrally formed with a plug-dropping head or canbe an auxiliary feature that is mounted to a plug-dropping head. Therelease mechanism is actuated by remote control, employing intrinsicallysafe circuitry. The circuitry, along with its self-contained powersource, actuates a primary control member responsive to an input signalso as to allow component shifting for release of the pumpdown plug orball. Multiple plug-dropping heads can be stacked, each responsive to adiscrete release signal. Actuation to drop the pumpdown ball or plug isaccomplished even while the components are rotating or are movinglongitudinally. Using the apparatus and method of the present invention,personnel do not need to climb up in the derrick to actuate manualvalves. There is additionally no need for a rig floor-mounted controlpanel with hydraulic lines extending from the control panel to remotelylocated valves for plug or ball release.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an existing prior art plug-dropping head for which apreferred embodiment has been developed.

FIGS. 2A and 2B illustrate the plug-dropping head of FIG. 1, with a fewparts removed for clarity, illustrated with the release mechanism of theapparatus and method of the present invention installed and ready torelease.

FIG. 3 illustrates the piston/cylinder combination in the initialposition before release of the plug.

FIG. 4 is the same piston/cylinder combination of FIG. 3 in the unlockedposition after plug release.

FIG. 5 is an end view of the view shown in FIG. 2, illustrating thespring action feature.

FIG. 6 is a detail of FIG. 1, showing the existing pin which is changedto accept the invention.

FIG. 7 is a sectional elevational part exploded view of the apparatus.

FIG. 8 is a sectional view of the apparatus showing the rack.

FIG. 9 is an electrical schematic representation of the transmitter usedin the invention.

FIGS. 10 and 11 represent the electrical schematic layout of thecomponents to receive the signal from the transmitter and to operate avalve to initiate release of a ball or plug.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a prior art plug-dropping head available from BakerOil Tools. The preferred embodiment of the apparatus and invention hasbeen configured to be mountable to the plug-dropping head illustrated inFIG. 1 as an addon attachment. However, those skilled in the art willappreciate that an integral plug-dropping head, with the remote-releasemechanism which will be described, can be provided without departingfrom the spirit of the invention.

In the prior design shown in FIG. 1, a top connection 1 is supportedfrom the derrick in the customary manner. Top connection 1 is connectedto a mandrel 9, which is in turn connected to a bottom connection 12.Inside mandrel 9 is sleeve 8. At the bottom of sleeve 8 is plug stop 10,which is connected by roll pin 11 to sleeve 8. In the position shown inFIG. 1, plug stop 10 would retain a ball or plug above it since itextends transversely into the central flowpath. With the sleeve 8 shownin the position in FIG. 1, flow bypasses a plug (not shown) which isdisposed atop plug stop 10. Flow which comes in through top connection 1circulates through a bypass passage 13 until it is time to drop the ballor plug. At that time, set screw 3 is operated and turned 180° manually.The turning of set screw 3 releases its hold on sleeve 8 and allowssleeve 8 to drop down. As a result of sleeve 8 dropping down, plug stop10 can pivot around roll pin 11 and the plug or ball is released.Additionally, sleeve 8 comes in contact with bottom connection 12,thereby sealing off bypass passage 13. Thereafter, circulation into topconnection 1 can no longer go through bypass passage 13 and mustnecessarily bear down on the ball or plug in the central port or passage15, which results in a pressure being applied above the plug or ball todrive it through bottom connection 12 and into the liner being cementedin the well.

As previously stated, the operation described in the previous paragraph,with regard to the prior art tool of FIG. 1, at times necessitatedsending personnel significant distances above the rig floor for manualoperation of set screw 3. Of course, rotation and longitudinal movementof the tool shown in FIG. 1 had to stop in order for set screw 3 to beoperated to release sleeve 8.

Referring now to FIG. 2, the tool in FIG. 1 is shown with many of thecomponent omitted for clarity. At the top, again, is top connection 1,which is connected to mandrel 9, which is in turn connected to bottomconnection 12. Sleeve 8 sits within mandrel 9, and pin 11 secures theplug stop (not shown) in the position to retain a ball or plug in theposition shown in FIG. 2. It should be noted that the tool shown in FIG.1 is in the same position when shown in FIG. 2. That is, the plug stop10 retains the plug while the flow goes around the sleeve 8, through thepassage 13. Ultimately, when sleeve 8 shifts, tapered surface 16contacts tapered surface 18 on bottom connection 12 to seal off passage13 and to direct flow coming into top connection 1 through the centralpassage 15 to drive down the ball or plug into the wellbore.

However, there is a difference between the assembly shown in FIG. 2 andthe assembly shown in FIG. 1. Set screw 3 of FIGS. 1 and 6 has beenreplaced by a totally different assembly which eliminates the manualoperation with respect to the embodiment shown in the prior art ofFIG. 1. Instead, a housing 20 has been developed to fit over topconnection 1 until it comes to rest on tapered surface 22. The housing20 has a mating tapered surface 24 which, when it contacts taperedsurface 22, longitudinally orients housing 20 with respect to topconnection 1.

Rotational orientation is still properly required. To accomplish this,at least one orienting groove or cutout 26 has been machined into topconnection 1. For each cutout 26 there is an alignment bore 28 inhousing 20. A bolt 30 is advanced through threaded bore 28 until itsticks into and firmly engages cutout 26. Once at least one bolt 30 isinserted into a cutout 26, the radial orientation between housing 20 andtop connection 1 is obtained. That orientation can be secured with setscrews (not shown) inserted through threaded bores 32 and 34. At thatpoint, not only is housing 20 properly oriented, but its orientation isproperly secure. As a result of such orientation, bore 36 in topconnection 1 is aligned with bore 38 in housing 20. Bores 36 and 38 aredisposed at an angle with respect to the longitudinal axis of topconnection 1. A preferably square thread 40 is located in bore 36.Instead of set screw 3 (see FIG. 6), a pin 42 (see FIG. 7) is installedthrough aligned bores 36 and 38. Threads 44 on pin 42 engage thread 40in bore 36.

FIG. 7 outlines the assembly procedures for the installation of pin 42.After aligning housing 20, as previously described, the cover 46 (seeFIG. 2) is removed, allowing access to bore 38 for installation of pin42. Pin 42 is advanced and rotated into threads 40 until tapered surface48 is in an orientation about 180° opposed from that shown in FIG. 7.The orientation of surface 48 is determined by the orientation of bore50, which does not extend all the way through pin 42. Bore 50 isdesigned to accept a handle 52 (see FIG. 2). The orientation of taperedsurface 48 is known by the orientation of bore 50. Having alignedtapered surface 48 in a position about 180° opposed from that shown inFIG. 7, the gear 54 is fitted over pin 42 and handle 52 is extended intobore 50. By extending handle 52 through catch 56 on gear 54, thelongitudinal positioning of gear 54 with respect to pin 42 isaccomplished. Additionally, the orientation of catch 56 allows initialrotation of both pin 42 and gear 54 to get them into the set positionshown in FIG. 2.

Prior to securing the gear 54 onto pin 42, a pair of split sleeves 58are fitted to housing 20 and secured to each other by fasteners 60. Arack 62 (see FIG. 8) is secured to sleeves 58 via fasteners 64 (see FIG.7).

As shown in FIG. 8, gear 54 meshes with rack 62 such that rotation ofpin 42 will rotate sleeves 58. Also connected to sleeves 58, as shown inFIG. 8, are lug or lugs 66. In the preferred embodiment there are twolugs 66 secured to sleeves 58 (see FIG. 5). Typically for each one, abolt 68 extends through a piston 70 to secure the piston 70 to lug 66(see FIGS. 5 and 8). The piston 70 is an elongated member that extendsthrough a cylinder 72 and is sealed thereto by O-ring seal 74. Disposedbetween piston 70 and cylinder 72 is floating piston 76, which is sealedagainst cylinder 72 by seal 78 and it is further sealed against piston70 by seal 80. A first port 82 allows fluid communication into cavity84, which is formed between cylinder 72 and piston 70 and between seal74 on piston 70 and seal 80 on floating piston 76. A second port 86 isalso disposed in cylinder 72 and communicates with cavity 88. Cavity 88is disposed between piston 70 and cylinder 72 on the other side of seal74.

Cylinder 72 has a mounting lug 90. Bolt 92 secures cylinder 72 in apivotally mounted orientation to housing 20.

Referring back to lugs 66, each has a bracket 94 (see FIG. 5) to securean end of spring 96. A lug 98 is rigidly mounted to housing 20 (see FIG.8) and secures the opposite end of spring 96. Spring 96 extends spirallyaround sleeves 58.

It should be noted that while one particular piston cylinder assemblyhas been described, a plurality of such identical assemblies or similarassemblies can be used without departing from the spirit of theinvention. There are two in the preferred embodiment. In essence, thepreferred embodiment illustrates the preferred way to accomplish adesired movement which is responsive to a particular signal for remoterelease of the ball or plug.

The first port 82 has a line 100 leading to a check valve 102 and acommercially available, intrinsically safe solenoid valve 104 mounted inparallel (see FIG. 3). The use of check valve 102 is optional. Comingout of solenoid valve 104 is line 106 which leads back to second port86. Cavities 84 and 88, as well as lines 100 and 106 are filled with anincompressible fluid. Solenoid valve 104 is electrically operated and isof the type well-known in the art to be intrinsically safe. This meansthat it operates on such low voltage or current that it will not induceany sparks which could cause a fire or explosion. The electricalcomponents for the apparatus A of the present invention are located incompartment 108 of housing 20 (see FIG. 8). A sensor 110 (see FIGS. 3and 8) is mounted in each of bores 112 in housing 20. Each of thesensors 110 is connected to the electronic control system 114. The powerfor the electronic control system 114 comes from a battery 116. Sensor110 receives over the air a signal 118 from a control 120. In thepreferred embodiment, the drilling rig operator holds the control 120 inhis hand and points it in the direction of sensors 110, which aredistributed around the periphery of housing 20 and oriented in adownward direction. The preferred embodiment has six sensors 110. Therig operator points the control 120, which is itself an intrinsicallysafe device, which emits a signal 118 that ultimately makes contact overthe air with one of sensors 110. The signal can be infrared or laser orany other type of signal that goes over the air and does not create anyexplosive fire or other hazards on the rig. The effect of a signal 118received at a sensor 110 is to actuate the control system 114 to opensolenoid valve 104.

However, prior to explaining the actuation of the release, the initialset-up of the apparatus A needs to be further explained. As previouslystated, pin 42 is installed in a position which is the fully releasedposition. That position is, in effect, about 180° different from theorientation shown in FIG. 2. With that initial installation, gear 54 issecured to rack 62. At that point in time, the cylinder 72 is disposedin the position shown in FIG. 4, with the spring 96 fully relaxed exceptfor any preload, if built in. When handle 52 is given a 180° rotation,it moves rack 62, which is connected to sleeves 58 as are lugs 66.Accordingly, 180° rotation of handle 52 has the net effect of rotatinglugs 66 away from bracket or brackets 98 about 30°-45°. The differencein position of lugs 66 with respect to bracket 98 is seen by comparingFIGS. 3 and 4.

As a result of the 180° rotation of handle 52, pin 42 is now in theposition shown in FIG. 2. By moving lugs 66 away from bracket 98, spring96 has been stretched. In order to accommodate the rotational movementinduced by handle 52, piston 70 must move to a position where it is moreextended out of cylinder 72. In making this movement, cavity 88 mustgrow in volume while cavity 84 shrinks in volume. As a result, there isa net transfer of fluid, which could be oil or some other hydraulicfluid, through conduit 100 as cavity 84 is reduced in volume, throughcheck valve 102, if used, and back into conduit 106 to flow into cavity88 which is increasing in volume. During this time, of course, floatingpiston 76 experiences insignificant net differential pressure and merelymoves to accommodate the change in volume of cavity 84. It should benoted that if check valve 102 is not used, the operator must use control120 to trigger valve 104 to open prior to rotating handle 52. This isbecause without check valve 102, if valve 104 remains closed, it willnot be possible to turn handle 52 because the rack 62 will not be freeto move because piston 70 will be fluid-locked against movement into orout of cylinder 72. Therefore, if an assembly is used without checkvalve 102, the operator must ensure that valve 104 stays open as theorientation is changed from that shown in FIG. 4 to that shown in FIG.3. In the preferred embodiment, a timer can be placed on valve 104 sothat when it is triggered to open by control 120, it stays open for apredetermined time (about 4 minutes), thus giving the components time tomake their required movements, both in the set-up and the release modes.

The result of the initial rotation of handle 52 about 180° in thepreferred embodiment is that pin 42 suspends sleeve 8, which keeps plugstop 10 supporting the ball or plug 122 (see FIG. 7).

When it is time to release the ball or plug 122, the operator, standingin a safe location on the rig floor, aims the control 120 toward sensors110. Having made contact over the air with a signal 118 transmitted fromcontrol 120 to one of the sensors 110, the control system 114 isactuated to open valve 104. When valve 104 is opened, the force inexpanded spring 96 draws lugs 66 rotationally toward bracket 98. This isallowed to happen as fluid is displaced from cavity 84 through line 100through valve 104 back through line 106 to cavity 88. As lug 66 rotatesdue to the spring force which is now no longer opposed by the hydrauliclock provided by having valve 104 in the closed position, the rotationof sleeve 58 rotates rack 62, which in turn rotates gear 54, which inturn rotates pin 42 from the position shown in FIG. 2 approximately 180°. This results in the release of sleeve 8 so that it can shiftdownwardly as previously explained. The downward shifting of sleeve 8allows plug stop 10 to pivot on roll pin 11, thus removing the supportfor the ball or plug 122. The ball or plug 122 can drop. Its downwardprogress toward the liner being cemented can also be assisted by pumpingdown on top of the plug due to passage 13 being cut off upon shifting ofsleeve 8, as in the original design shown in FIG. 1.

It should be noted that the housings 20 can be stacked in series, eachequipped with sensors 110 that respond to different signals so that ifthere is a stack of housings 20 in use for a particular applicationrequiring several plugs to be dropped, the sensitivity of sensors 110 ondifferent housings 20 to different signals ensures that the plugs aredropped in the proper order. Accordingly, a separate controller 120 isprovided for each apparatus A to be used in series, and aiming onecontroller with a discrete signal to a sensor 110 will not actuate theapparatus A unless the specific signal that sensor 110 is looking for isreceived. Alternatively, a single controller 120 can be programmed togive different signals 118 in series to accomplish release in the propersequence.

The control 120 is further illustrated in FIG. 9. Control 120 comprisesa hand-held transmitter having several components. The transmitterincludes a tone generator 101, which generates a multiplicity offrequencies. In the preferred embodiment, the tone generator 101generates 5 frequencies comprising 150 Hz, 300 Hz, 600 Hz, 1200 Hz, and2400 Hz. Additionally, the tone generator 101 creates a carrierfrequency of 38 kHz. The frequencies generated by the tone generator101, except for the carrier frequency, are passed through amicrosequencer 103, and ultimately to a mixer 105 where the carriersignal is mixed with the other frequencies generated. The mixed signalis then passed to an amplifier or power driver 107 for ultimatereception at sensors 110 (see FIG. 10). As can be seen from the tablewhich is part of FIG. 9, a four-button selector is provided on thetransmitter control 120. The first frequency sent, regardless of thecombination selected, is 150 Hz, and the last signal sent is 2400 Hz. Itshould be noted that selecting different signal combinations on thecontrol 120 will result in actuation of a different ball or plug 122 inan assembly involving a stack of units.

Referring now to FIG. 10, any one of the sensors 110 can pick up thetransmitted signal and deliver it to the pre-amp and demodulator 109.The carrier frequency of 38 kHz is eliminated in the pre-amp anddemodulator, and the individual frequency signals sent are sensed by thevarious tone decoders 111. Each of the tone decoders 111 are sensitiveto a different frequency. When the tone decoder for the 150 Hz detectsthat frequency, it resets all of the latches 113. The latches 113 emit abinary output dependent upon the input from the tone decoders 113. Whenthe last frequency is detected, that being the 2400 Hz frequency at thedecoder 111, the latch 113 associated with the decoder for the 2400 Hzfrequency enables the decoder 115 to accept the input from the remaininglatches 113 to generate a suitable output which will ultimately triggervalve 104 to open. Again, depending on the binary input to the decoder115, discrete signals result as the output from decoder 115, whichresult in a signal transmitted to one shot 117, shown in FIG. 11. Theone shot 117 triggers a timer 119, which in the preferred embodiment isset for keeping the valve 104 in the open position for 4 minutes. Thesignal to timer 119 also passes to solenoid driver 121, which is aswitch that enables the solenoid 123 to ultimately open valve 104. As asafety precaution to avoid release of any ball or plug 122 if the powersupply becomes weak or is otherwise interrupted, there is a power on/offdetector 125, which is coupled to a delay 127. If the available powergoes below a predetermined point, the solenoid 123 is disabled fromopening. Thereafter, if the power returns above a preset value, therequirements of time in delay 127 must be met, coupled with a subsequentsignal to actuate solenoid 123, before it can be operated. The powersupply to the control circuits is provided by a plurality of batteriesthat are hooked up in parallel. These batteries are rechargeable and aregenerally recharged prior to use of the assembly on each job. Thebatteries singly are expected to have sufficient power to conclude thedesired operations.

In another safety feature of the apparatus, in making the initialrotation of handle 52 to set the apparatus A up for release, if for anytime during the rotation of handle 52 it is released, check valve 102will prevent its slamming back to its original position due to spring96, which could cause injury to personnel. By use of check valve 102,the initial movement of handle 52 is ensured to be unidirectional sothat it holds its ultimate position when released simply because thefluid in the circuit in lines 100 and 106 cannot flow from conduit 106back to conduit 100 with check valve 102 installed and solenoid valve104 closed.

It should be noted that the preferred embodiment having beenillustrated, the scope of the invention is broad enough to encompassalternative mechanisms for creating the necessary motion to release aball or plug 122 by virtue of a remote, over-the-air signal.

The foregoing disclosure and description of the invention areillustrative and explanatory thereof, and various changes in the size,shape and materials, as well as in the details of the illustratedconstruction, may be made without departing from the spirit of theinvention.

We claim:
 1. A control system useful in outdoor environments,comprising:a primary control element operating in a system; at least onetransmitter for sending a predetermined plurality of frequencies overthe air; at least one signal receiver for receiving said predeterminedplurality of frequencies from said transmitter to provide an output; atleast one signal processor to receive the output of said receiver and togenerate a command signal to said control element; at least one of saidfrequencies serving a dual purpose of being first part of a receivedsignal sent to said processor to allow said processor to issue an outputsignal to operate a primary controlled element, and second to act as acue to said processor that an incoming multiple frequency signal isabout to come or has concluded; and said processor discriminates forsaid frequencies and generates an output signal to said primary controlelement based on the order of frequencies received.
 2. A well controlsystem, comprising:a primary control element operating in a well system;at least one transmitter for sending a predetermined plurality offrequencies order over the air; at least one signal receiver forreceiving said predetermined plurality of frequencies from saidtransmitter to provide an output; at least one signal processor toreceive the output of said receiver and to generate a command signal tosaid control element; at least one of said frequencies serving a dualpurpose of being first part of a received signal sent to said processorto allow said processor to issue an output signal to operate a primarycontrolled element, and second to act as a cue to said processor that anincoming multiple frequency signal is about to come or has concluded;and said processor discriminates for said frequencies and generates anoutput signal to said primary control element based on the order of thefrequencies received.
 3. The apparatus of claim 1, wherein:at least afirst and second frequency serve a dual purpose and are part of asequence of signals that triggers an output from said processor; saidfirst frequency is first in time and cues said processor that amultifrequency signal is arriving, said second frequency is last in timeand cues said processor that a multifrequency signal is fullytransmitted, thus triggering said processor to issue an output signalfor actuation of the primary controlled element.
 4. The apparatus ofclaim 3, wherein:said receiver further comprises a self-contained powersupply; interlock means on said power supply to prevent actuation of theprimary controlled element unless a preset value of power exists for apreset time.
 5. The apparatus of claim 2, wherein:at least a first andsecond frequency serve a dual purpose and are part of a sequence ofsignals that triggers an output from said processor; said firstfrequency is first in time and cues said processor that a multifrequencysignal is arriving, said second frequency is last in time and cues saidprocessor that a multifrequency signal is fully transmitted, thustriggering said processor to issue an output signal for actuation of theprimary controlled element.
 6. The apparatus of claim 5, wherein:saidreceiver further comprises a self-contained power supply; interlockmeans on said power supply to prevent actuation of the primarycontrolled element unless a preset value of power exists for a presettime.